Rotor wing shielding compensation method for helicopter satellite communication

Abstract

The invention provides a rotor wing shielding compensation method for helicopter satellite communication, and relates to the technical field of helicopter communication methods, and the method comprises the following steps: collecting angular velocity data in real time through a rotor wing main shaft sensor, constructing a rotating speed state equation, and providing accurate input for phase prediction; predicting a rotor phase based on an extended Kalman filter; a dynamic time slot distribution function is designed, so that the communication time slot length is automatically adjusted along with the rotation speed change of the rotor; a non-linear phase error caused by rotor vibration is counteracted through a feed-forward compensation item; closed-loop time calibration of a communication protocol and a mechanical system is realized by adopting double PID controllers. According to the method, real-time closed-loop synchronization of a mechanical system and a communication protocol is realized by establishing a three-dimensional mapping relation of rotor rotating speed-phase-communication time slot, so that the problem of nonlinear error accumulation during dynamic change of the rotating speed is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopter communication methods, and particularly relates to a method for compensating for rotor occlusion in helicopter satellite communication. Background Art

[0002] Satellite communication (referred to as satellite communication for short) has the advantages of wide frequency band, large capacity, stable performance, and cost independent of communication distance, and has become an important means of modern communication. Helicopter satellite communication refers to the direct communication between a helicopter and a satellite through airborne satellite equipment, and the transmission and exchange of information with a ground station through the relay of the satellite.

[0003] However, due to the periodic occlusion of the helicopter rotor, the signal attenuation shows non-linear fluctuations, and a time calibration mechanism for real-time matching of the mechanical speed and the communication protocol is required. In the existing related technologies, the anti-rotor occlusion algorithms are mostly based on fixed-period models, but the speed change can reach ±15% when the helicopter switches between hover / cruise states, resulting in the accumulation of dynamic modulation errors. Summary of the Invention

[0004] In order to solve the technical problems in the related technologies, the present invention provides a method for compensating for rotor occlusion in helicopter satellite communication. The present invention realizes the real-time closed-loop synchronization of the mechanical system and the communication protocol by establishing a three-dimensional mapping relationship of rotor speed-phase-communication time slot, and solves the problem of non-linear error accumulation when the speed changes dynamically.

[0005] In order to achieve the above object, the technical solutions adopted by the present invention include: The present invention provides a method for compensating for rotor occlusion in helicopter satellite communication, including the following steps: Step S1: Real-time collect angular velocity data through a rotor main shaft sensor, and construct a speed state equation to provide accurate input for phase prediction; Step S2: Predict the rotor phase based on an extended Kalman filter; Step S3: Design a dynamic time slot allocation function to automatically adjust the communication time slot length according to the rotor speed change; Step S4: Cancel the non-linear phase error caused by rotor vibration through a feed-forward compensation term; Step S5: Use a dual PID controller to realize the closed-loop time calibration of the communication protocol and the mechanical system.

[0006] Optionally, the specific steps of step S1 include: Step S1-1: Real-time collect angular velocity data through a rotor main shaft sensor; Step S1-2: Construct a speed state equation: Where is the angular acceleration, is the moment of inertia of the rotor, is the driving torque of the rotor motor, is the damping coefficient, is the angular velocity of the rotor, is the load torque, , 、 is the aerodynamic coefficient, calibrated by wind tunnel experiments.

[0007] Optionally, the step S1-2 further includes: extracting the rotational speed spectrum features by using a sliding window Fourier transform to filter high-frequency noise.

[0008] Optionally, the step S2 specifically includes: using an improved extended Kalman filter to estimate the rotor phase in real time: In the formula, is the predicted phase at the th moment, is the phase at the th moment, is the sampling time interval, is the estimated value of the angular acceleration at the th moment, is the angular acceleration at the th moment, is the jerk at the th moment.

[0009] Optionally, in the step S3, the dynamic time slot allocation function is: In the formula, is the communication time slot length, is the fundamental frequency of the rotor, , is the adjustment factor, and its value range is from 0.2 to 0.5, is the change in rotational speed, , is the current actual rotational speed, is the rated rotational speed, is the rotational speed change threshold.

[0010] Optionally, the rotational speed change threshold is set to 5% of the rated rotational speed.

[0011] Optionally, the step S4 specifically includes: Step S4-1: Construct a feedforward compensation term: In the formula, is the phase compensation amount, is the harmonic order, is the speed-phase coupling coefficient, which is calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, and its value range is from 1 to M, is the time variable; Step S4-2: Cancel the non-linear phase error caused by rotor vibration through the feedforward compensation term: In the formula, is the compensated phase, is the predicted phase.

[0012] Optionally, in the step S5, The dual PID controller equation is: In the formula, is the control output, that is, the driving motor torque adjustment amount, , and are the PID gain parameters respectively, is the phase error, and , is the measured phase, is the predicted phase; According to Dynamically adjust the communication transmitter clock source to achieve time alignment.

[0013] Optionally, the rotor occlusion compensation method for helicopter satellite communication further includes: Step S6: Verify the time calibration accuracy according to the following formula: In the formula, is the root mean square error of the time calibration accuracy, is the total number of calibration times, is the th timestamp of the communication protocol, that is, the moment when the satellite communication device plans to send or receive a signal, is the th timestamp of the mechanical system, that is, the actual moment when the rotor occlusion state allows communication.

[0014] Beneficial effects: 1. Through the above technical solutions, first, compared with the traditional fixed-cycle model, this solution can maintain a small time calibration error during hover / cruise switching through dynamic time slot allocation and dual PID control, and can effectively improve the dynamic adaptability.

[0015] Second, the present invention actively cancels the non - linear phase error caused by rotor vibration through the feed - forward compensation term, thereby effectively reducing phase jitter, which is equivalent to effectively improving the signal - to - noise ratio.

[0016] Third, the present invention adopts a time - frequency cooperation mechanism of extended Kalman filtering and dynamic time - slot allocation, enabling the time reference of the communication protocol to be synchronized with the mechanical rotation speed at the sub - millisecond level, thereby effectively reducing the communication error rate.

[0017] Generally speaking, through the technical path of "dynamic modeling - predictive compensation - closed - loop control", the present invention can achieve three major mutations: joint modeling in the time - frequency domain, non - linear feed - forward compensation, and adaptive communication protocol.

[0018] 2. Other beneficial effects or advantages of the present invention will be described in detail in the specific implementation manner. Brief Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Among them: Figure 1 is a schematic flow chart of the steps of the rotor occlusion compensation method for helicopter satellite communication provided by an exemplary embodiment of the present invention. Detailed Description of the Embodiments

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0023] In addition, the terms "comprising" and "having" and any variations thereof mentioned in the description of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include other steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products, or devices. It should also be noted that in the embodiments of the present invention, words such as "exemplary" or "for example" are used to represent examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0024] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] As Figure 1 shown, the present invention provides a method for compensating for rotor occlusion in helicopter satellite communication, including the following steps: Step S1: Real-time collect angular velocity data through a rotor main shaft sensor, construct a rotational speed state equation, and provide accurate input for phase prediction; Step S2: Predict the rotor phase based on an extended Kalman filter; Step S3: Design a dynamic time slot allocation function to automatically adjust the communication time slot length according to the rotor speed change; Step S4: Cancel the non-linear phase error caused by rotor vibration through a feed-forward compensation term; Step S5: Use a dual PID controller to achieve closed-loop time calibration of the communication protocol and the mechanical system.

[0026] Through the above technical solution, first, compared with the traditional fixed-cycle model (when the rotational speed fluctuates by ±15%, the error accumulation can reach 27 μs), this solution can maintain a small time calibration error (for example, ≤15 μs as described below) during hover / cruise switching through dynamic time slot allocation and dual PID control, and can effectively improve the dynamic adaptability.

[0027] Second, the present invention actively cancels the non-linear phase error caused by rotor vibration through a feed-forward compensation term, thereby effectively reducing the phase jitter, which is equivalent to effectively improving the signal-to-noise ratio.

[0028] Third, the present invention adopts a time-frequency cooperation mechanism of extended Kalman filtering and dynamic time slot allocation, enabling the time reference of the communication protocol and the mechanical rotational speed to maintain sub-millisecond synchronization, thereby effectively reducing the communication error rate.

[0029] Generally speaking, through the technical path of "dynamic modeling - predictive compensation - closed-loop control", the present invention can achieve three major breakthroughs: joint modeling in the time-frequency domain (unifying mechanical rotational dynamics and communication protocol time bases under the extended Kalman filter framework), non-linear feedforward compensation (establishing a dedicated compensation function for the periodic occlusion unique to the rotor), and adaptive communication protocol (initially creating a dynamic time slot allocation function, enabling the communication system to effectively adapt to a certain degree of rotational speed fluctuations).

[0030] In one embodiment of the present invention, step S1 of the present invention may specifically include: Step S1-1: Real-time collect angular velocity data through a rotor main shaft sensor; Step S1-2: Construct a rotational speed state equation: In the formula, is the angular acceleration, is the rotor moment of inertia, is the rotor motor drive torque, is the damping coefficient, is the rotor angular velocity, is the load torque, , , are aerodynamic coefficients, calibrated by wind tunnel experiments.

[0031] In this way, in this embodiment, the present invention real-time collects rotor rotational speed data through a sensor and establishes a comprehensive mathematical model including mechanical load and aerodynamics, providing an accurate input for phase prediction.

[0032] Specifically, in the existing related technologies, the rotor load is mostly simplified to a constant damping model, ignoring the non-linear characteristics of aerodynamics, resulting in a large load error in the hover state. In this embodiment, through the term represents the quadratic relationship between air resistance and rotational speed, accurately reflecting the strong non-linear coupling (such as the vortex ring state) between the rotor and the airflow during hover. At the same time, through the term models the periodic occlusion effect of a four-blade rotor (4π corresponds to 4 occlusions per revolution), and the absolute value operation captures the non-directional characteristics of the occlusion amplitude. Thus, the load torque prediction error can be effectively reduced, and the phase prediction accuracy can be improved.

[0033] In this embodiment, it should be noted that, first, for the aerodynamic term ( ), its design principle is: when the rotor rotates, the air resistance is proportional to the square of the rotational speed (and the rotational speed is proportional to the angular velocity), so this term can reflect the main power consumption in the hover state. At the same time, for For the calibration of parameters, the torque-speed curve can be measured at different rotational speeds according to wind tunnel experiments, and determined by fitting using the least squares method. ( The typical value range is from 0.05 to 0.2 ).

[0034] Second, for the periodic occlusion term ( ), its design principle is: each rotation of the four-blade rotor generates 4 occlusions (frequency ), and the absolute value operation converts the sine wave into a full-wave rectified waveform, matching the non-negative value characteristic of the actual occlusion signal. At the same time, for For the calibration of parameters, on the occlusion test bench, the occlusion time ratio between the rotor and the antenna can be recorded by a laser rangefinder, and ( The typical value range is 0.3 - 1.2 ) can be inversely calculated.

[0035] In an embodiment of the present invention, step S1-2 of the present invention may further include: extracting the rotational speed spectrum characteristics by using the sliding window Fourier transform to filter out high-frequency noise.

[0036] In this way, in this embodiment, through the dynamic adjustment of the time-frequency analysis window (such as the window length adaptively matching the current rotational speed), high-frequency noise introduced by rotor vibration, transmission gear meshing, etc. can be effectively filtered out (for example, noise > 200 Hz, which is because in the existing related technologies, the rotor signal often mixes high-frequency noises such as transmission gear vibration and engine jitter, and the existing fixed-bandwidth low-pass filter will mis-cut the effective harmonic components). Among them, the design of the sliding window can effectively avoid spectrum leakage caused by a fixed window (for example, when the rotational speed changes), while retaining the rotational speed transient characteristics.

[0037] In an embodiment of the present invention, step S2 of the present invention may specifically include: Using an improved extended Kalman filter to estimate the rotor phase in real time: In the formula, is the predicted phase at the th moment, is the phase at the th moment, is the sampling time interval, is the estimated value of the angular acceleration at the th moment, is the angular acceleration at the th moment, is the angular jerk at the th moment.

[0038] Thus, in this embodiment, the present invention proposes a phase prediction model that fuses angular acceleration and angular jerk to solve the problem of prediction lag in traditional methods when the rotational speed changes suddenly.

[0039] Specifically, in this embodiment, the present invention uses an improved extended Kalman filter. Based on the traditional extended Kalman filter, a third-order Taylor expansion and angular jerk compensation are introduced to improve the dynamic accuracy of rotor phase prediction. First, the standard extended Kalman filter uses a first-order Taylor approximation. When the helicopter's rotational speed changes rapidly (e.g., a ±15% rotational speed step), the prediction error caused by non-linear terms above the third order is relatively large. The improved extended Kalman filter of the present invention adds a third-order term (i.e., angular jerk j), so that in the scenario of sudden rotational speed changes (e.g., hovering to cruise), the phase prediction error can be effectively reduced. Second, the third-order model is closer to the actual dynamics of the rotor and can expand the filter bandwidth and shorten the step response time. Third, through the active compensation of the high-frequency jitter by the angular jerk term, under certain vibration noise power conditions, the phase prediction variance can be reduced and the system stability can be improved.

[0040] In this embodiment, it should be noted that First, as an integral quantity of the rotation angle, the discrete-time recursion of the rotor phase needs to consider high-order derivatives: , where the angular velocity is the phase change rate (first-order term), the angular acceleration is the rotational speed change caused by torque imbalance (second-order term), and the angular jerk reflects the torque change rate (third-order term), corresponding to the rapid adjustment of the motor drive torque during helicopter maneuvers. Thus, due to the strong non-linearity of helicopter rotor dynamics, the third-order expansion is closer to the Taylor series characteristics of the real system, and thus the linearization error can be effectively reduced.

[0041] In an embodiment of the present invention, in step S3 of the present invention, the dynamic time slot allocation function is: In the formula, is the communication time slot length, is the rotor fundamental frequency, , is the adjustment factor, and its value range is from 0.2 to 0.5, is the rotational speed change amount, , is the current actual rotational speed, is the rated rotational speed, is the rotational speed change threshold.

[0042] Thus, in this embodiment, the present invention designs a dynamic time slot allocation function, which can automatically stretch and shrink the communication time slot length according to the change of the rotor speed, avoiding the signal being blocked by the rotor.

[0043] Specifically, first, the dynamic time slot allocation function ( ) can adjust the communication time slot length in real time according to the change of the rotor speed ( ), so as to effectively solve the communication interruption problem caused by the traditional fixed-cycle model when the speed fluctuates by ±15%, and can effectively adapt to the scenario of sudden speed change.

[0044] Second, the present invention realizes the step-free adjustment of the time slot length through the hyperbolic tangent function ( ), avoiding the data packet conflict caused by the time slot mutation. When is close to the threshold , the change rate of the time slot length is the largest, and when , the adjustment amplitude tends to saturation ( ), ensuring the system stability.

[0045] Third, the reference time slot length ( ) corresponds to the periodic characteristic (frequency ) of the four-blade rotor blocking 4 times per revolution, making the communication time slot naturally aligned with the mechanical blocking event, so as to effectively reduce the bit error rate of satellite communication.

[0046] In this embodiment, it should be noted that, First, for the hyperbolic tangent function ( ), when , , the time slot adjustment linearly responds to the minute speed change; when , , the time slot length reaches the maximum adjustment value , preventing over-adjustment.

[0047] Second, for the adjustment factor, its value range (0.2 to 0.5) can be calibrated by wind tunnel experiments. Among them, when, it can ensure that when the speed changes by 5%, the time slot adjustment amplitude ≥ 4% ( ), avoiding insufficient sensitivity; when, it can prevent overshoot when the speed suddenly changes (for example, when the corresponding time slot length increases by 38% ), avoiding communication protocol overrun.

[0048] In an embodiment of the present invention, the speed change threshold of the present invention can be set to 5% of the rated speed.

[0049] Thus, setting the speed change threshold to 5% of the rated speed (i.e., ), which not only effectively filters out high-frequency jitter in the rotor transmission system (for example, gear meshing noise ±2%), but also shortens the response time (relative to a fixed threshold design) of threshold-triggered time slot adjustment during hover / cruise switching (speed variation ±15%). Furthermore, it avoids frequent fine-tuning of time slot length (for example, speed fluctuation ±3%), reducing the power consumption of clock calibration in the communication system.

[0050] In one embodiment of the present invention, step S4 of the present invention may specifically include: Step S4-1: Construct feedforward compensation term: Where, is the phase compensation amount, is the harmonic order, is the velocity-phase coupling coefficient, calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, which ranges from 1 to M. is the time variable; Step S4-2: offset the nonlinear phase error caused by rotor vibration through the feedforward compensation term: Where, is the phase after compensation, The predicted phase is the output of the improved extended Kalman filter from the previous article, which is used to characterize the ideal motion trajectory of the rotor. The compensation term It corrects high-frequency vibration errors that are not covered by the improved extended Kalman filter, forming a dual correction architecture of "prediction + compensation".

[0051] Thus, in this embodiment, the feedforward compensation term designed by the present invention can offset the high-order harmonic interference, thereby resolving the non-periodic phase disturbance caused by rotor vibration.

[0052] Specifically, conventional linear compensators exhibit high residual jitter under fourth-order harmonic interference (rotor vibration causes periodic phase jitter), which can cause communication bit error rates to soar. However, the method of this invention limits phase jitter through a feedforward compensation term, thereby improving the signal-to-noise ratio and effectively reducing communication bit error rates.

[0053] Second, the present invention The function limits the compensation frequency band to only It takes effect nearby and can effectively avoid interference with other frequency bands (for example, the frequency band of navigation signals).

[0054] Third, the order M of the Taylor series expansion of the present invention is adjustable, which can adaptively match the main vibration harmonics of the four-blade rotor, thereby effectively improving the compensation efficiency.

[0055] In this embodiment, it should be noted that First, for the Taylor series terms ( ), an odd-power design is first performed, and only the odd terms ( ) are retained to match the asymmetry of the rotor vibration phase (for example, the transient difference between the occluded / non-occluded states). Its physical meaning is: approximating the phase error caused by rotor vibration , and its Taylor expansion coefficient is related to the vibration amplitude (speed-phase coupling coefficient).

[0056] Second, for the sinc function modulation ( ), the spectrum of the sinc function is a rectangular window, which can ensure that the compensation energy is concentrated within the communication frequency band. At the same time, it can also suppress the interference of high-frequency vibration noise (such as engine vibration) on the compensation signal.

[0057] Third, for the calibration of the speed-phase coupling coefficient , it can be calibrated through a wind tunnel experiment. Fix the rotor speed and measure the cumulative amount of phase error over time, and use the least squares method to fit and determine , and its typical value range is: 0.05 - 0.3 rad(m / s).

[0058] Fourth, for the selection of the harmonic order M, since the main vibration energy of the four-blade rotor is concentrated in , , and other integer multiples of 4 frequencies. When M = 4, the first 4 harmonics (4 to 16 times the fundamental frequency) can be covered, and the compensation efficiency is relatively high; while higher orders (for example, M > 6) have limited improvement on the system performance and increase the calculation amount.

[0059] In an embodiment of the present invention, in step S5 of the present invention, The dual PID controller equation is: In the formula, is the control output, that is, the driving motor torque adjustment amount, , and are the PID gain parameters respectively, is the phase error, and , is the measured phase, is the predicted phase; According to Dynamically adjust the clock source of the communication transmitter to achieve time alignment.

[0060] In this embodiment, the present invention realizes microsecond-level time synchronization between the mechanical system and the communication protocol through a dual PID controller, suppressing cumulative errors.

[0061] Specifically, first, the single PID controller in the prior art is prone to overshoot (the peak value of the phase error reaches 25 μs) during helicopter maneuvers (for example, a ±15% sudden change in rotational speed), which may cause communication interruption. The dual PID controller of the present invention reduces the root mean square value of the calibration error through frequency band division control, thereby improving the accuracy and avoiding the problem of communication interruption.

[0062] Second, the parallel structure of the dual PID controller of the present invention can expand the system bandwidth (compared to a single PID), shorten the response time of the step change in rotor speed, and improve the dynamic response speed to meet the tactical maneuvering requirements.

[0063] Third, the present invention suppresses high-frequency vibration noise through the differential term. Under the interference of the fourth-order harmonic, it can reduce the variance of the control output, thereby significantly improving the system stability.

[0064] In this embodiment, it should be noted that First, based on the dual PID controller equation of the present invention, it can be known that the architecture design of the dual PID includes: Drive loop PID: In the formula, is the output of the drive loop, is the proportional term coefficient of the drive loop (i.e., the proportional gain parameter), is the integral term coefficient of the drive loop (i.e., the integral gain parameter), is the differential term coefficient of the drive loop (i.e., the differential gain parameter); among them, can be set relatively large (for example, 2.5 ) to quickly respond to the rotational speed deviation, is used to suppress the mechanical oscillation caused by the sudden change of the motor torque; to achieve the adjustment of the rotor motor torque , maintaining the rotational speed stability (against the load torque fluctuation).

[0065] Time base loop PID: In the formula, is the output of the time base loop, is the proportional term coefficient of the time base loop (i.e., the proportional gain parameter), is the integral term coefficient of the time base loop (i.e., the integral gain parameter), is the derivative term coefficient of the time base loop (i.e., the derivative gain parameter); where dominates (e.g., 0.8 ) to eliminate the clock cumulative error, and cooperatively suppress the time jitter of the communication protocol; thus realizing the adjustment of the clock source frequency of the communication transmitter to synchronize the time slot allocation with the rotor phase.

[0066] Among them, the output of the drive loop is used as the feedforward input of the time base loop to cancel the disturbance of the motor torque adjustment to the clock synchronization, so that the adjustment amount of the time base loop can be reduced; at the same time, the drive loop is used to control the rotational speed stability of the low frequency band (e.g., 0 to 5 Hz), and the time base loop is used to control the clock synchronization accuracy of the high frequency band (e.g., 5 to 20 Hz). The frequency domain components of the error signal are separated by a band-pass filter to achieve the decoupling of the control objectives.

[0067] That is to say, the drive loop maintains the stability of the mechanical system, and the time base loop ensures the synchronization of the communication protocol. The two are dynamically coupled through the feedforward channel to reduce the overshoot of the system step response.

[0068] Second, the present invention also has an integral anti-windup mechanism (when the phase error continuously exceeds the threshold, e.g., 10 μs, the accumulation speed of the integral term is limited, which can prevent the system instability caused by the overflow of the control quantity) and differential noise filtering (a first-order low-pass filter can be added to the differential channel to suppress the amplification effect of the high-frequency noise of the sensor on the term, thereby reducing the noise power).

[0069] In an embodiment of the present invention, the rotor occlusion compensation method for helicopter satellite communication of the present invention further includes: Step S6: Perform time calibration accuracy verification according to the following formula: In the formula, is the root mean square error of the time calibration accuracy, is the total number of calibration times, is the th time stamp of the communication protocol, that is, the moment when the satellite communication device plans to send or receive a signal, is the th time stamp of the mechanical system, that is, the actual moment when the rotor occlusion state allows communication.

[0070] In this way, through the root mean square error verification method, it can be ensured that the time synchronization accuracy between the communication protocol and the mechanical system meets the stringent standard.

[0071] Specifically, first, the time synchronization error ≤ 15 μs, which can accurately avoid the rotor occlusion window in the communication time slot, thereby reducing the communication interruption rate and optimizing the bit error rate. That is to say, it can achieve high-reliability communication guarantee.

[0072] Second, this index ( ) is not only a performance index, but also defines the error allocation budget of each sub-module (or step) described above (for example, the sum of errors such as the improved extended Kalman filter prediction error and the time slot allocation error should not exceed ), which is conducive to guiding system-level optimization.

[0073] The steps of the present invention will be described below in conjunction with an exemplary implementation manner.

[0074] Step 1: Dynamic rotational speed monitoring Scenario setting: The helicopter switches from the hover state (rated rotational speed = 300 RPM = 31.42 rad / s) to the cruise state, and the actual rotational speed fluctuates to = 345 RPM = 36.13 rad / s.

[0075] Parameter setting: The rotor moment of inertia = 5.2 (unit is ), the damping coefficient = 0.8 (unit is ), the aerodynamic coefficient = 0.015, = 0.2 (calibrated by wind tunnel experiment); Calculation process: 1. Calculate the load torque : Assume = 0.1 s, substitute it into = 6.13 rad / s, then there is: Calculate the angular acceleration : Assume the rotor motor drive torque = 25 (unit is ), according to the state equation, then there is: Output: angular acceleration .

[0076] Step 2: Dynamic phase prediction Parameter setting: = 0.001 s (sampling interval); Parameter at the previous moment: = 12.5 rad, = 35.0 rad / s, , ; Substitute into the prediction equation: It can be calculated that ; Output: Current predicted phase .

[0077] Step 3. Adaptive adjustment of communication protocol Parameter setting: Hz, , (5% of the rated speed), ; Calculation process: Substitute into the dynamic time slot allocation function: It can be calculated that .

[0078] Output: Adjusted communication time slot length .

[0079] Step 4. Nonlinear error compensation Parameter setting: , , , , calculate the compensation term ; Calculation process: Substitute into the feedforward compensation formula: Among them, the step-by-step calculation process: 1、 (Because the high-frequency oscillation approaches zero); 2. Series term: , ; , ; , ; Total sum ; Then the final compensation amount Output: Compensation amount (Due to the high-frequency carrier causing the sinc function to approach zero).

[0080] Step Five, Closed-loop feedback calibration Parameter setting: , , ; Measured phase , Predicted phase Calculation process: 1. Calculate the phase error: 2. Calculate the PID output (assuming the integral term is initially 0 and the derivative term is the error change rate): It can be calculated that Output: Control amount, driving the motor to reduce the torque to correct the phase.

[0081] Step Six, Performance verification Calculation of time calibration accuracy: Assume the time deviation for 10 calibrations is: Then the root mean square error is: Conclusion: Meets the performance index requirements.

[0082] In this exemplary embodiment, when the helicopter speed increases from 300 RPM to 345 RPM, through steps such as dynamic phase prediction, time slot adjustment, and closed-loop calibration, the time synchronization error of 11.9 μs can be finally achieved, which is significantly better than the traditional method.

[0083] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A rotor occlusion compensation method for helicopter satellite communication, characterized in that It includes the following steps: Step S1: Collect angular velocity data in real time through the rotor main shaft sensor, construct a rotational speed state equation, and provide accurate input for phase prediction; Step S2: Predict the rotor phase based on the extended Kalman filter; Step S3: Design a dynamic time slot allocation function to automatically adjust the communication time slot length according to the change of the rotor speed; Step S4: Cancel the non-linear phase error caused by the rotor vibration through the feed-forward compensation term; Step S5: Adopt a dual PID controller to achieve the closed-loop time calibration of the communication protocol and the mechanical system.

2. The rotor occlusion compensation method for helicopter satellite communication according to claim 1, characterized in that The specific content of step S1 includes: Step S1-1: Collect angular velocity data in real time through the rotor main shaft sensor; Step S1-2: Construct a rotational speed state equation: In the formula, is the angular acceleration, is the moment of inertia of the rotor, is the driving torque of the rotor motor, is the damping coefficient, is the angular velocity of the rotor, is the load torque, , , are aerodynamic coefficients calibrated by wind tunnel experiments.

3. The method for compensating for rotor occlusion in helicopter satellite communication according to claim 2, wherein The step S1-2 also includes: Extract the rotational speed spectrum characteristics by using the sliding window Fourier transform to filter out high-frequency noise.

4. The rotor shielding compensation method for helicopter satellite communication according to claim 2, characterized in that, The specific content of step S2 includes: Adopt an improved extended Kalman filter to estimate the rotor phase in real time: Wherein, is the predicted phase at the th moment, is the phase at the th moment, is the sampling time interval, is the estimated value of the angular acceleration at the th moment, is the angular acceleration at the th moment, is the angular jerk at the th moment.

5. The method for compensating for rotor occlusion in helicopter satellite communication according to claim 4, wherein, In step S3, the dynamic time slot allocation function is: Wherein, is the communication time slot length, is the fundamental frequency of the rotor, , is the adjustment factor, and its value range is from 0.2 to 0.5, is the change in rotational speed, , is the current actual rotational speed, is the rated rotational speed, is the rotational speed change threshold.

6. The method for compensating for rotor shielding in helicopter satellite communication according to claim 5, wherein The rotational speed change threshold is set to 5% of the rated speed.

7. The rotor occlusion compensation method for helicopter satellite communication according to claim 5, characterized in that The specific content of step S4 includes: Step S4-1: Construct a feed-forward compensation term: In the formula, is the phase compensation amount, is the harmonic order, is the speed-phase coupling coefficient, which is calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, and its value range is from 1 to M, is the time variable; Step S4-2: Cancel the non-linear phase error caused by the rotor vibration through the feed-forward compensation term: Wherein, is the compensated phase, is the predicted phase.

8. The rotor shielding compensation method for helicopter satellite communication according to claim 7, characterized in that In step S5, The dual PID controller equation is: Wherein, is the control output, i.e., the driving motor torque adjustment amount, , and are respectively the PID gain parameters, is the phase error, and , is the measured phase, is the predicted phase; According to Dynamically adjust the communication transmitter clock source to achieve time alignment.

9. The method for compensating for rotor shielding in helicopter satellite communication according to claim 8, characterized in that, The rotor occlusion compensation method for helicopter satellite communication also includes: Step S6: Verify the time calibration accuracy according to the following formula: In the formula, is the root mean square error of the time calibration accuracy, is the total number of calibration times, is the th timestamp of the communication protocol, that is, the moment when the satellite communication device plans to send or receive signals, is the th timestamp of the mechanical system, that is, the actual moment when the rotor occlusion state allows communication.

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